1. Field of the Invention
The invention relates to a rotary cutting tool, such as a drilling head or the like, and more particularly concerns a rotary cutting tool comprising a tool body having a bearing surface, at least one cutter carrier, a cutting element at one end of the, or each, cutter carrier, and a fastening screw means for clamping the, or each, cutting element to the bearing surface of the tool body, the bearing surface being provided with a tooth formation which extends transversely to the longitudinal axis of the tool body and the underside of the cutter carrier being provided with a tooth formation engageable with the tooth formation on the bearing surface.
2. Description of the Prior Art
Drilling heads constructed as so-called double cutters for drilling out drill holes are known, in which two cutter carriers are each radially displaceable and can be be secured in the adjusted position with one or two fastening screws. The bearing surface for the cutter carrier on the tool body is in this case often provided with a tooth formation, with which a corresponding tooth formation on the underside of the cutter carrier engages. Bearing surfaces of this type for cutter carriers in known designs either have a similar tooth formation on the front end of a tool body for both cutter carriers or there are toothed bearing surfaces at an angle to one another. The fastening screw, which either penetrates an oblong hole in the cutter carrier and is screwed into a borehole in the tool body or passes through a round hole in the cutter carrier and then engages in a nut which is displaceable in the tool body, is always perpendicular to the toothed bearing surface. The tooth formation has in all cases a symmetrical design, i.e. both flanks of a tooth are in each case at the same angle relative to a median plane.
The tooth formation together with the fastening screw must transmit the forces occurring in the cutting process from the cutter carrier to the tool body. As has been seen, considerable effects of force occur partly in this connection, which tend to shift the cutter carrier out of the tooth formation. Furthermore, the main cutting force or the resultant from the cutting forces, in particular the main cutting force and advancing force, particularly in the case of cutter carriers displaced radially outwards to varying degrees, causes bending of the cutter carrier. The result of this is that the cutter carrier moves upwards on its bearing surface and when the force subsides springs immediately downwards again, which leads to vibration during machining.
The cutter carriers are often very narrow, and tilting then occurs which is caused by the main force and which exerts considerable tensile stress upon the fastening screw. If the distance of the cutting plate from the displacement plane of the cutter carrier is relatively large, a large bending moment must be absorbed by the fastening screws when loads occur. Such large moments can under certain circumstances even lead to a lengthening of the screws, which can result in a loosening of the cutter carrier and thus destroy the tool. The existing narrowed spatial conditions in tools of the type in question and limits in the material strength are considerable obstacles, which hitherto prevented a satisfactory solution.